The three primary approaches used to clean commercial and residential carpets are steam or hot water, foam and dry systems. Dry-type carpet cleaning systems are further divided into two broad categories, namely, those using a dry or substantially dry powder and those using granules which are slightly moistened with cleaning solvents for dirt removal. The inventive machine has utility for both categories of dry systems but relates primarily to those using granules rather than powder. Such machine also has utility in situations where only carpet vacuuming is performed. That is, its aggressive, long-bristled brushes are highly effective in removing loose sand and other soil not requiring the application of solvent-bearing material.
Of the dry granular carpet cleaning systems, the best known and most widely used is the HOST.RTM. dry extraction system offered by Racine Industries, Inc. of Racine, Wis. The HOST.RTM. system applies granules to carpet fibers using a machine as shown in Rench et al. U.S. Pat. Nos. 2,842,788 and 2,961,673. Such machine, sold under the HOST.RTM. trademark, is devoid of vacuum capability and has a pair of spaced brushes counter-rotating at relatively low speed (about 350 rpm) to stroke the cleaning granules into, through and across carpet fibers. The granules are referred to as "dry" and are substantially so even though moistened with cleaning solvents. When stroked as described, these granules "scrub" soil and dirt from such fibers including oily and non-oily soil. The carpet is cleaned by working the HOST.RTM. machine across it in different directions. During the cleaning process, granules migrate to the carpet backing adjacent the base of the fiber. A few granules also adhere lightly to the fibers along their lengths. Following cleaning, conventional carpet vacuum machines are used for removing the dirt-ladened granules.
Because of the way they are constructed, conventional vacuum machines are not ideally suited for the removal of such dirt-ladened granules although such machines do a reasonably acceptable job of such removal. In particular, most such machines employ a single "beater bar" which rotates at high speed and which uses spaced rows of relatively short bristles. A few such machines have two beater bars which are constructed and operate in much the same way. Such high speed beater bars with short bristles are more effective in removing granules near the tops of the fibers but significantly less so as to granules which are "deep down" in the carpet.
Another disadvantage of such machines is that the beater bars are driven by smooth-surfaced, flexible rubber belts which wrap partially around the bar. The solvent used to moisten the granules often causes the belt to slip, thereby temporarily disabling the beater bar.
Further, the embodiment of carpet brushing and carpet vacuuming capabilities in two separate machines means that both such machines must be available to complete the cleaning process. This represents an extra equipment expense and for the professional carpet cleaner, it also represents added time (reflected in employee wages) required to get the necessary machines to the job site and to later remove such machines. Examples of conventional vacuum machines are shown in U.S. Pat. Nos. 1,891,504 and 4,426,751.
One type of machine used to apply dry cleaning powder to carpet fiber is made by Clarke-Gravely Corporation of Muskegon, Michigan and sold as the CLARKE CAPTURE carpet cleaning system. Such machine distributes cleaning powder onto the carpet and works the powder into and through the carpet fibers using a round, disk-like scrubber brush, the axis of rotation of which is normal to the carpet surface. The machine vacuum system operates to reduce dust. After cleaning, a separate conventional vacuum machine is used to remove the powder.
Another type of system used for cleaning carpets with powder is the DRYTECH cleaning machine sold by Sears, Roebuck & Company. The machine has a self-contained vacuum capability and one beater bar with several rows of short-bristled brushes. Such bar is within a shroud which generally conforms to the shape of the bar and by which vacuum is selectively applied. As the brush alone is rotated at high speed, powder is dispensed through two slits, one on either side of the bar between the bar and the shroud. Later, the vacuum is actuated and dry powder (with dirt entrained) is dislodged by the brush and drawn away by vacuum.
Several patents show machines which combine brush and vacuum features for removing dirt from a surface. Although such machines are described as being used to clean hard surfaces such as uncarpeted floors, streets and cisterns, there are certain characteristics worthy of mention. For example, the machine shown in Bentley U.S. Pat. No. 1,759,881 uses spaced counter-revolving brushes and two vacuum inlet passages. Each passage is defined by a scraper blade and one side of a V-shaped deflector. Material scraped from a brush by a blade is drawn into the vacuum inlet The inlets are positioned at that part of the brush contacted by the scraper, presumably for the purpose of immediately "capturing" material dislodged by the scraper. The brushes and vacuum operate simultaneously.
A machine used to clean out tanks is shown in Murray et al. U.S. Pat. No. 715,408. The Murray machine uses spaced counter-revolving brushes and a vacuum tube, the nozzle of which is at the location where the brushes are in closest proximity to one another.
A street and lawn sweeping machine is shown in Keyes U.S. Pat. No. 755,596. The Keyes machine has separate support wheels, a pair of contacting, counter-revolving brushes and an exhaust fan to carry away dirt. The vacuum inlet opens at a location above and in general registry with the line of contact of the bristles on the brush rollers.
A type of cleaning machine is also shown in German Patent DE 33 16847 A1. Such machine uses a pair of spaced, counter-revolving brushes with spaced rows of bristles. A vacuum nozzle extends the length of the brushes and apparently has two panels, each of which is in contact, or nearly in contact, with a brush. The brushes and vacuum appear to operate simultaneously.
A street cleaning machine is shown in Duthie U.S. Pat. No. 1,069,773 and has a pair of counter-revolving brushes, each of which is substantially confined within its own shroud. Each shroud has a vacuum tube connected thereto for dirt removal.
A vacuum cleaning tool is shown in Bayless U.S. Pat. No. 3,753,263. The Bayless tool uses separate support wheels and a pair of counter-rotating beater bars fitted with rigid vanes or with brushes. A vacuum nozzle is positioned between the bars and in close proximity to the carpet. The tool is said to separate the fibers of deep pile shag rugs so that the vacuum nozzle may extract dirt therefrom.
None of the machines discussed above provide the advantages of a dual machine capability to first apply dry carpet cleaning granules to a carpet for cleaning its fibers and later remove the dirt-ladened granules from the carpet using one or more vacuum nozzles which are independently operable. Further, the designers of such machines failed to appreciate how such vacuum nozzles can advantageously be positioned to take advantage of the granule "throw pattern" for most efficient granule removal.
That is, as a carpet is being cleaned using dry granules, such granules are thrown or cast from the tips of the brush bristles along trajectories generally tangent to the brush and generally perpendicular to (but spaced from) the axis of rotation of the brush. Some of these granules are cast against the shroud which covers the brushes and define a "throw pattern" on the bottom surface of such shroud. Such throw pattern may be a single, generally rectangular area positioned directly above the space between the brushes or such pattern may comprise two such areas which are spaced apart from one another.
Earlier workers in this field have failed to understand how one or more vacuum nozzles may be positioned in the shroud to be generally coincident with such throw pattern, thereby providing a more efficient vacuuming capability. A machine having relatively low speed, long-bristled, counter-revolving brushes for first applying dry carpet cleaning granules in the absence of vacuum and later using the combined action of the brushes and the independently operable vacuum to remove the granules from the carpet would be an important advance in the art.